Preparation of medical fluid for extracorporeal blood treatment typically involves adding one or more substances (e.g. NaCl or CaCl) to a base fluid (e.g. water). The base fluid is typically drawn from a fluid source, for example a fluid line or a tank. One or more substances are then added to the fluid, typically by conveying at least a portion of the fluid through one or more substitutable containers holding the one or more substances.
The adding of substances may be achieved in several separate stages, where one or more substances are added to the fluid at each stage. The stages are typically arranged in series such that fluid prepared at one stage is subsequently conveyed through another stage. However, other layouts or setups are possible (e.g. stages being arranged in parallel).
At each stage, typically, a flow controller (e.g. a valve or a pump) conveys a predetermined amount of fluid into and/or through the container, thereby dissolving or otherwise carrying a desired amount of the substance or substances present in the container with the fluid and out of the container. The containers typically contain the one or more substances as salts or liquids. After at least a portion of the fluid has been directed through the container and has dissolved an amount of the one or more substances and has exited the container, the fluid is mixed with the remainder of the fluid in a common or main fluid line. In cases where separate sources of fluids are used (e.g. a main fluid source providing the main fluid flow, and a separate fluid source supplying fluid to one or more stages) the fluid exiting a stage is then mixed with the base fluid coming from a (separate) main fluid source.
Downstream from the stage or stage(s), typically, one or more sensors (e.g. conductivity sensors, optical sensors, or other) are arranged so as to measure the concentration of the one or more substances in the fluid. Based on the concentration(s) measured, the respective flow controller(s) may be controlled to increase or decrease the respective flow of fluid through the respective container in order to achieve and/or maintain a desired concentration of each of the one or more substances.
Downstream from the last stage, typically, one or more filters (e.g. ultrafilters) are employed in order to remove any unwanted particles and/or substances in the fluid. Typically, at least two filters are employed in order to provide two-stage safety and avoid a single point of failure. In particular, when infusion fluid is prepared and provided for pre- and/or post-dilution, at least two ultrafilters are employed to provide infusion fluid having the required composition and purity for being infused into the vascular system of a patient.
The one or more substances are typically provided (e.g. in the form of salt or dry or wet concentrate) in a cartridge or container that is designed to operably couple to the preparation apparatus. The containers are provided with an inlet port and an outlet port, thereby allowing a fluid to enter the container, to dissolve or otherwise take up some of its contents, and to exit the container.
The container or containers are installed before fluid preparation commences and/or replaced during fluid preparation, for example when their contents are depleted. The installation or coupling requires the apparatus to have a corresponding coupling system.
Before installation of the containers and/or after preparation of fluid (e.g. before storage or when a unit is scheduled for downtime), the fluid lines of the apparatus require priming and/or cleaning, disinfection, etc. During the respective process (e.g. priming), typically no containers are installed at the different stages. In order to facilitate the process, the respective coupling ports (which would be connected to respective inlet and outlet ports of a container during operation) need to be connected to a bypass line of some kind, so that fluid (e.g. priming fluid) can pass through the respective main lines, branch lines, and connectors.
In some examples, the coupling system includes two arms pivotably connected to the apparatus and each carrying a coupling port configured for coupling with a corresponding inlet or outlet port of the cartridge or container. The two arms are further capable of assuming at least a retracted position, in which the coupling port is connected to a corresponding bypass port and a bypass line of the apparatus. This position allows for priming, disinfection, cleaning, or other procedures when no container is installed and/or when the apparatus is not in operation (e.g. preparing a fluid). Also, if the apparatus comprises several stages for the optional installation of several containers, not all stages need to be in use, depending upon the type of fluid to be prepared.
A single two-arm stage typically has a single bypass line comprising two bypass ports, wherein the two arms may be positioned or configured so that the coupling ports are secured and connected to the bypass ports, thereby defining a closed loop from a bifurcation on the main fluid line where fluid is drawn, through an intake line and a pump, as well as through the coupling port, bypass port, bypass line, another bypass port, another coupling port, and through an outlet line back to another bifurcation, feeding the fluid back into the main fluid line.
In the retracted position, a proper connection between the coupling ports and the bypass ports needs to be ensured, so that no fluid can leak from the circuit and no foreign substances can contaminate fluid flowing through the circuit.
In order to ensure a proper connection the coupling ports and the bypass ports, different systems have been devised. In one example, a proximity sensor (e.g. a reed switch) is configured to sense the proximity of the arm carrying the coupling port, generating a corresponding signal for a control unit to process. In another example, a mechanical switch (e.g. a micro switch) is actuated upon the arm carrying the coupling port being locked into proper position.
A key issue of known systems includes a proper adjustment or calibration of the sensors. On one hand, the system should ensure that an improperly configured arm is accurately detected, so that operating personnel may be made aware of an inadequate connection between any of the coupling ports and bypass ports. On the other hand, false alarms should be avoided as much as possible, such that the apparatus can be operated with a high efficiency.
Proximity switches need to be properly positioned and configured in order to detect the position of an arm with the required accuracy and reliability. Mechanical switches also require proper placing and adjustment and are prone to contamination by foreign substances (e.g. dust, dirt, particles). Mechanical switches may also be difficult to clean.
EP 0458041 discloses an apparatus for preparation of dialysis fluid in connection with haemodialysis and for preparation of replacement fluid in connection with haemofiltration or haemodiafiltration, which has lever arms and a by-pass line.
EP 1049497 discloses a holder for a powder cartridge in a dialysis machine and describes safety considerations in connection with the holder and the use of powder cartridges. Separate holders for the cartridges are also described. Sensors can detect whether the holders are folded out and contain a cartridge.
It is an object of the present invention to render available an apparatus for the preparation of fluids designed to limit improper positioning of the one or more movable members configured to hold the container of one or more substances.
Additionally, it is an auxiliary object of the invention an apparatus configured to allow reliably detecting an incorrect configuration (e.g. if one or more movable members are not properly locked in their retracted position), thereby ensuring proper connection of the corresponding ports and preventing contamination of the circuit and leakage of fluids.
It is a further object of the invention to render available an apparatus, which reduces the number of false alarms and improves the rate of detection (e.g. minimizing failed detections).
It is a further object of the invention to provide a method of setting up a medical apparatus for the preparation of fluids, which improves the reliability of the process of connecting and disconnecting containers.
It is a further object of the invention to provide a method of using a medical apparatus for the preparation of fluids.
It is a further object of the invention to render available an extracorporeal blood treatment apparatus comprising a medical apparatus for the preparation of fluids.